1. Field of the Invention
This invention relates to surface controlled subsurface safety valves used in the oil and gas industry, and more particularly, to a lockout housing and sleeve for a tubing retrievable safety valve.
2. Description of Related Art
It is common practice to complete oil and gas producing wells with systems including a subsurface safety valve controlled from the well surface to shut off fluid flow in the well tubing string. Such a valve is generally controlled in response to control fluid pressure conducted to the valve from a remote location at the well surface via a small diameter conduit, permitting the well to be selectively shut in as well conditions require.
Conventional surface controlled subsurface safety valves have previously been disclosed, for example, in U.S. Pat. Nos. 4,723,606 and 4,945,993. As shown in FIG. 2A of U.S. Pat. No. 4,723,606, such valves have previously utilized a lockout sleeve, and threaded knockout plugs to hold the lockout sleeve in its inactive position during normal operation of the safety valve. If the safety valve becomes inoperative, the lockout sleeve can be forced downward to open the valve. Downward movement of the lockout sleeve causes the threaded plugs to shear, establishing hydraulic fluid communication from the control line through the orifice in the portion of each sheared plug that remains threadedly engaged with the lockout housing.
During use of surface controlled subsurface safety valves comprising conventional lockout sleeves and housings, fluid leaks sometimes develop around the threaded shear plugs, especially when the plugs are subjected to repeated hitting that can cause them to crack or fail prematurely.